Galaxy part 3

Star Populations in the Galaxy

       Stars as the object in this universe has different characteristics such as size, shape, mass, luminosity, and age. There is a relationship between the characteristics of stars with a place in the galaxy. Young star around the age of several million years, illuminates the spiral arms of our galaxy. These stars are stars that are brighter and the blue group occupies in the main sequence. Strong radiation of interstellar gas clouds shining such as fog Horse Head (horsehead Nebula). Half stars age, around the age of several billion years, evenly distributed throughout the disc, while old stars, with age more than 10 billion years, scattered around the disk which appears in the halo and core regions (the galactic center region).

       Of the stars that make up this galaxy, about half of a double star system (binary) or a star system where two or more stars there are in a mutually orbiting systems caused by traction grafitasinya. Many stars are also bound together by gravity that form clusters (clusters) that contain hundreds of thousands of stars in the region of hundreds of light years or more. Our galaxy alone contains 400 billion stars with a range of about 100,000 light years.

       Giant all-star who is very bright, and main sequence stars with high luminosity (classes O and B) and type I Chepeid stars contained in the region of interstellar matter in the spiral arms of galaxies. Medium types of other stars has nothing to do with his place in the galaxy, such as planetary nebulae, nova, Chepeid type II, Lyrae variable stars, and globular clusters. Main sequence star class F and M, as well as red giants and white dwarfs are in all parts of the galaxy.

       Similarly, chemical composition, there is a difference of stars whose position is different in the galaxy. Sun and other stars are related to the interstellar matter of the spiral arms have heavy elements of about 1-4% of the total mass of stars. Medium galaktika halo stars and globular clusters, has a heavy element is much less about 0.1 to 0.01 of the sun.

       The stars that inhabit the spiral arms is often said to include population I, while the other is in place in the galaxy is said to include population II. Population I consists of stars with different ages, including a new star or who is undergoing formation. Medium population II consists entirely of old stars, maybe even the formation of our galaxy's age.